Batch Size selection for Scale-up & Feasibility Study

Because of my stringent schedules, Can't check the comments and sorry for not replying to those, Apart from that i'm quite happy as followers were getting increased day to day, in parallel it was desperate as i'm not getting any author requests.

Anyway, recently i've received a mail from a Process Engineer working in one of the top Pharma company, his name is Mr. Ram Prakash, and the query is,

"How to select a batch size during scale up ? As mostly management is not interested in going for green field projects, how to select a appropriate batch size ?"

So, as per me the query is slightly a common issue, because in the early stages of process engineering during learning about scale-up techniques there will be lots and lots of things, but while coming to implementation, a process engineer should always think in company's favour and the decision that is taken should be in company's interest. As management always want high returns with low investments.

Rookie Process Engineer's may not accept this, but after gaining some experience one should accept it.

Scale-up's are most common in industries with certain amount of risk. Always there will be a some risk under every task, But a process engineer is treated as a true professional when the executed scale-up get succeeded with calculated risk. For that there may be many ways, out of which Power per unit volume is a basic and traditional path. Everyone knows that, but mostly not applied practically .

Mostly the equipment selection shall be done based on availability (no offense to anyone). But the scale-up batch size selection most probably rests with a process engineer. And the available chance need to be capitalised properly.

Lets start with a case study, Consider a reaction and we need to scale it up.

Let it be some condensation / dehydration reaction.

and initially the reaction [35 Kg batch size] is carried out in a 500 L SSR in small scale.

2000 L SSR is available for Scale-up, Agitator remains the same as PBT.

Below is the Calculation :

Parameters

UOM

Values

Formulae

Reactor Capacity (REV)

L

500

-

Batch Size (B)

Kg

35

-

Reaction mass volume (RV)

L

265.3

7.6 volumes

% Occupancy (O%)

-

53.06

REV/V

Cylindrical height (H)

m

0.865

-

Reactor ID (D)

m

0.815

-

L/D

-

1.06134969

H/D

Agitator Dia (d)

m

0.46

-

% sweep (S%)

-

56.4417178

(d/D)*100

Torispherical Volume (Tv)

m3

0.04817956

0.089x(D^3)

Cylindrical Volume (Cv)

m3

0.45102538

0.785x(D^2)xH

Volume in Cylindrical section (Rcv)

m3

0.26525182

(Rv-Tv)/1000

Cylindrical height of Rxn. Mass (Rh)

m

0.50871378

Rcv/(0.785x(D^2))

L/D for RM

-

0.62418868

Rh/D

Agitator type

-

PBT

-

Np

-

5

-

RPM

-

96

-

RPS (N)

rps

1.6

RPM/60

Density of the Rxn. Mass ®

Kg/m3

780

-

P

J/S

329.013496

Np x r x (N^3) x (D^5)

P

KW

0.3290135

P/1000

V

m3

0.2653

Rv/1000

P/V

KW/m3

1.24015641

P/V

So as per the batch size of 35 Kg, the power per unit volume is 1.24 KW/Cu.m.

Now, we need to consider some random batch sizes, [ kindly don't ask me how to consider those random too, that depends on our common sense],and perform the same calculation like we have done for 35 Kg batch size,

Parameters

UOM

Values

Formuale

Capacity

L

2000

-

Batch Size

Kg

70

80

90

95

100

110

120

-

Reaction mass volme

L

530.6

606.4

682.2

720.1

758

833.8

909.6

7.6 volumes

% Occupancy

-

26.53

30.32

34.11

36.01

37.9

41.69

45.48

REV/V

Cylindrical height

m

1.79

1.79

1.79

1.79

1.79

1.79

1.79

-

Reactor ID

m

1.4

1.4

1.4

1.4

1.4

1.4

1.4

-

L/D

-

1.28

1.28

1.28

1.28

1.28

1.28

1.28

H/D

Agitator Dia

m

0.56

0.56

0.56

0.56

0.56

0.56

0.56

-

% sweep

-

40

40

40

40

40

40

40

(d/D)*100

Torispherical Volume

m3

0.244

0.244

0.244

0.244

0.244

0.244

0.244

0.089x(D^3)

Cylindrical Volume

m3

2.754

2.754

2.754

2.754

2.754

2.754

2.754

0.785x(D^2)xH

Volume in Cylindrical section

m3

0.53

0.606

0.682

0.72

0.758

0.834

0.909

(Rv-Tv)/1000

Cylindrical height of Rxn. Mass

m

0.345

0.394

0.443

0.468

0.492

0.542

0.591

Rcv/(0.785x(D^2))

L/D for RM

-

0.25

0.28

0.32

0.33

0.35

0.39

0.42

Rh/D

Agitator type

-

PBT

PBT

PBT

PBT

PBT

PBT

PBT

-

Np

-

5

5

5

5

5

5

5

-

RPM

-

96

96

96

96

96

96

96

-

RPS (N)

rps

1.6

1.6

1.6

1.6

1.6

1.6

1.6

RPM/60

Density of the Rxn. Mass

Kg/m3

780

780

780

780

780

780

780

-

P

J/S

879.76

879.76

879.76

879.76

879.76

879.76

879.76

Np x r x (N^3) x (D^5)

P

KW

0.88

0.88

0.88

0.88

0.88

0.88

0.88

P/1000

V

m3

0.53

0.61

0.68

0.72

0.76

0.83

0.91

Rv/1000

P/V

KW/m3

1.66

1.45

1.29

1.22

1.16

1.06

0.97

P/V

After performing the calculation, it is clear that power per unit volume of only three batch sizes 90, 95, 100 Kgs were comparable to that of standard, and remaining four batches were out of bounds.

So, the conclusion is that if we are proceeding with 2000 L SSR, 90 Kgs, 95 KGs, 100 Kgs batch size is preferable and can be proceeded with calculated risk.

26 comments:

Dear ajay, its nice post shared by you...but by increasing the RPM we can match power per unit volume ratio.as you mentioned above formulae P=Np x r x (N^3) x (D^5 RPM is only parameter that can be vary & it directly proportion to power.

Great catch, but in some cases when you want to carry out reaction in Base mode then increasing RPM will have serious effect on agitator coupling, in that case if you want to enhance RPM then you need to increase torque, for that the shaft dia should be increased and the motor capacity should be more.

So one change will have impact on many things, which need to be carefully evaluated.

Dear Ajay,Please send the post if possible on solvent recovery & what are the parameters to be set like feed rate,Reflux rate ,Bottom temp & Top temp of column etc consider basically azeotropic Distillation.

Im working in process engineering department, one of the reaction i am handing reactants to products conversion time 43 hrs(Reaction time ), I have to increase the productivity with out changing the reactor for that i need to reduce the total reaction time for that

what are the calculation are required in engg points of you to increase the productivity and reduce the time cycle On what parameters can i make the changes Can you please explain by taking the example

What type of reaction is that ? What are the type of byproducts that are formed during the reaction ? whether they are washable in later stages or not ? If possible share the brief process, so that i can help you.

The question is clear, and i'll tell you far clear answer,Pharma directly implies manufacturing, in a manufacturing industry always the production department is king, and all other departments are supportive departments to production.And coming to our role, as a supporting team our job is to provide some momentum to production through 1. Speed(time-cycle reduction of the manufacturing operations), 2. Robustness(address the loopholes in the manufacturing operations), 3. innovations(implementing new techniques which can produce higher outputs through minimum inputs), 4. Recoveries(enhancing the reuse potential of the solvents), 5. Cost improvements(Reducing the excess raw materials consumption through optimization),6. Safety(Eliminating the existing hazards in the manufacturing process which acts as bottle necks), 7. Quality management(Enhancing the quality measures to improve/optimize the output quality).

I think the above mentioned things are a part of our chemical engineering. So a chemical engineer, these are our responsibilities in Pharma.If nay queries contact me through the contact me page.

Dear sir, When we need to scale up from lab scale to pilot scale we need to consider the lab scale stirrer blade power number to calculate the power/vol value. right? So can you please suggest me how much should I take for lab scale stirrer blade?

Usually it is very difficult to scale up from lab scale to pilot scale, because while coming to higher batch sizes in plant scale, we need to select facility based on availability. Mostly in Lab scale they will use Half moon agitator and RBF for experiments, so we can't judge / match the L/D ration of RBF and reactor.

So never scale up from lab to pilot[that's my suggestion], based on the MOC and based on the scale of agitation select the reactor & RPM,If required we can match power per unit volume from pilot to plant large scale.

If nay queries feel free to comment / contact me through the Contact me Page available at top of the page.

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Hi! I am Ajay Kumar Kalva, Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology.